Electron discharge device



A ril 30, 1946.

B. J. EDWARDS ELECTRON DISCHARGE DEVICE Fi led March 31 'mvsufonATTORNEYS Patented Apr. 30, 1946 ELECTRON DISCHARGE DEVICE Baden J.Edwards, Cambridge, England, assignor to Pye Limited, Cambridge,England, a British company Application March 31, 1944, Serial No.528,985 In Great Britain December 18, 1942 12 Claims.

This invention relates to electron discharge devices, and moreespecially to such devices having multi-control electrodes by which themixing of a number of waveforms can be effected, such as is necessary inmulti-channel telephone systems. The invention has for its object toprovide an improved device which is especially useful for mixingwaveforms but which may also have other applications in the electric andcommunications arts.

An electron discharge device embodying the present invention has anelectron, source or cathode spaced from an output electrode or anode,the cathode and anode being common to a group of similar controlelectrodes or grids which are disposed in closeproximity to the commonanode in the space between the cathode and anode so that each grid is.spaced the same distance as the others from the cathode and anode, andscreening electrodes being disposed partitioncorresponding parts.

wise between the grids so as to screen each grid 7 from the others.These screens may be grounded or connected to a low potential when thedevice is in operation. In such a device when in operation, a fractionof the electron stream fromthe cathode is controlled by each grid, eachof which may have one of the signals to be mixed applied thereto. Theinter-grid screens are provided to reduce grid interaction (theso-called Miller effeet) to negligible proportions. Control of theproportion appearing at the anode of each input signal may be effectedby controlling the bias of each of the grids, or for this purposefurther control electrodes may be included in the device.

Various constructional forms of the invention are possible, and by wayof example in the accompanying diagrammatic drawing Fig. 1 isa view inelevation of one form of electron discharge device constructed inaccordance with the invention, with the multi-control electrode assemblydepicted as a section taken on the line l--l of Fig. 2;

Fig. 2 is a plan view of the multi-control electrode assembly;

Fig. 3 is a plan view taken on line 3-3 of Fig. 1 showing the layout ofthe lead-in pins in the base of the device;

Fig. 4 is a view in elevation of another embodiment of the invention;

- Fig. 5 is a plan view taken on line 5--5 of Fig. 4 showing-the layoutof the lead-in pins in the base of the device of Fig. 4;

Figs. 6, 7 and 8 are views corresponding respectively to Figs. 1, 2 and3showingthe' device Referring to Figs. 1 to 3, an electron dischargedevice according to the invention is depicted having a plane-parallelarrangement of electrodes,

in which a substantially flat electron emitter or cathode .C of theequipotential type provided with an internal heating element H ismounted horizontally in the evacuated glass envelope E of the device andparallel with the base B. Spaced above the cathode Q and in parallelrelation thereto is a group (designated by G in Fig. 1) of similarcontrol electrodes or grids G1 Gs, disposed side by side in a circle ofwhich the individual grids constitute sectors separated from one anotherby narrow gaps to as to be insulated from one another. In the radialgaps between adjacent sectorial grids are disposed partitioning screensD which may be imperforate and may be made of metal sheet or strip. Thescreens D are shown disposed in vertical planes perpendicular to theplane of the sectorial grid array and extending sufiiciently above andbelow that plane to ensure effective screening of the grids from oneanother; In operation, the screens D may be grounded or connected tochassis or to a low potential and, therefore, may be conductivelyconnected together within the device, for instance by an encirclingmetal band or ring secured to their outer extremities to form awheel-like structure as shown, whereby the screens D may be allconnected to the same potential by a single conductor leading from thescreen structure. On the side remote from the cathode of the grid array.G and in close.- proximity to the latter is mounted in parallelismtherewith a substantially fiatcommonanode A.

The device is shown constructed with a moulded glass base B havingsealed through it stiff lead-in pins, generally indicated by P, uponwhich the cathode, grid and screen structures are supported by stiffwire leads welded to the electrodes and pins. The grids G1 G9 arerespectively connected to pins PG1 PGQ in'a circular array near theperiphery of the base B, as shown in Fig. 3. The cathode C and itsheater H are respectively connected to pins PC and PH in the centre ofthe base B. The screen structure D may be connected to the cathode pinPC (as indicated in Fig. l) or to one of the heater pins PI-I. Afterinserting the electrode assembly mounted on the base B into the envelopeE, the latter is sealed to the glass base. The anode A is separatelysupported by a stiff lead L which is taken out through the top of theenvelope E.

Instead of a plane-parallel electrode arrange ment, a coaxial electrodearrangement, as depicted in the embodiment of Figs.'4 and 5 may beemployed. The electrode structure in this case includes a centralcylindrical cathode 0 arranged vertically within the evacuated envelopee of the device, the cathode depicted being of the equipotential typeprovided with an internal heater h. Coaxially surrounding the cathode cis a group of similar control electrodes 91 g9 constituted by separaterings or short spiral sections superposed in a column and equally spacedapart along the length of the cathode 0. These control electrodes may bemade of wire or formed from metal sheet or strip. Interposed between theelectrodes 91 ye are annular or disc-like partitioning screens d whichmay be made from metal sheet or strip. Surrounding the column ofelectrodes 01 g9 and coaxial therewith and with the cathode c is thecommon anode a in th form of a sheet metal cylinder.

As in the case of the embodiment of Fig. 1, the device of Fig. 4 isshown constructed with a moulded glass base 17 having a circular arrayof lead-in pins poi p479 sealed-therethrough which are connectedrespectively to the electrodes g1 99. Also, the cathode c and its heaterh are respectively connected to lead-in mixing electrodes 91 G1 Gs, ofsectorial form and are disposed each immediately above and opposite thecorresponding one of the mixing grids. The screens D screen not only thegrids of the set G but also those of the set S from one another. Themoulded base B1 of the device is provided with an additional circulararray of lead-in pins PS1 PS9 connected respectively to the electrodesS1 So.

'In a corresponding manner, as depicted in Figs. 9 and 10, the device ofFigs. 4 and 5 may be provided with a second group of control electrodess1 so of similar construction to the mixing electrodes 91 g9 andpositioned between the latter and the cylindrical anode a1 so that theycoaxially surround and lie opposite the g9 respectively. The base In orthe device is provided with an additional circular array of lead-in pinsps1 ps9 connected respectively to the electrodes s1 so.

The number of mixing electrodes which may be mounted in a singleenvelope is, of course, restricted by mechanical considerations, but upto ten mixing electrodes with separating screens Although specificembodiments have been described, various constructional modificationsmay pins pc and ph sealed through in the centre of the base I), andlikewise the screens (1 are connected together and to either the pin pcor one of the pins ph. The anode lead I is again taken out through thetop of the envelope e of the device.

The described devices operate as waveform mixers by connecting each ofthe channels to be mixed between the cathod and individual mixingelectrodes G1 G9 or or yr. The presence of a potential on any electrodeof the group causes the electron streambetween cathode and anode to bemodulated in the vicinity of that mixing electrode. This control islimited, since only a fraction of the electron stream is be made thereinand other constructional forms devised within the scope of the inventionas defined by the appended claims. For instance, in a furthermodification of the specific embodiments described and illustrated inthe drawings, the screens D or d, as the case may be, are not connectedtogether within the device as hasbeen described and shown, but are leftinsulated from one another and are respectively connected to a separateset of lead-in pins or conductors additionally provided for the purpose,so that the screens can be individually connected to suitable potentialsand separately controlled. Thus. in the case of the devices of Figs. 1and 6, this modification means that the encircling band connectingscreens D together would be omitted and replaced by leads to theindividual screens brought out of the envelope separately, throughadditional pins in the base or through the en- 1 velooe elsewhere.

affected by each mixer, but this is of no great signifiicance in adevice designed s ecially for mixing. The device according to thisinvention may be used in any apparatus where it is desired to mix two ormore signals. and the proportion of each input signal appearing at theanode may be controlled by controlling the biassing potential of each ofthe mixin electrodes. Such control of the mixing may be effected inanother way by means of further control electrodes included in thedevice especially for this purpose.

and base B1 are made somewhat larger than their counterparts in thedevice of Fig. l. The further control grids Si S9 are, like gridsIclaim:

1. In an electron discharge device, an electron emitting cathode, agroup of similar control electrodes, a cooperating anode" common to saidgroup of control electrodes, said anode being spaced from said cathodeand located to receive the electron stream emitted by said cathode, saidgroup of control electrodes being disposed in the space between saidcathode and anode and spaced from one another and similarly located withreso'ect to said cathode for each, independently of the others, tomodulate a fractionof the total electron stream received by said'commonanode from said cathode. and screening electrodes disposedpartition-wise in the spaces between said control electrodes to formcompartments in which said control electrodes are respectively situated,to screen each of said control electrodesanode, screening electrodesdisposed partitionwise between said control electrodes so as to screeneach of them from the others, and a second group of control electrodesdisposed in the space between said first group and said anode with theelectrodes of said second group opposite those of said first grouprespectively.

3. In an electron discharge device, a substantially fiat cathode spacedfrom a substantially flat cooperating anode parallel therewith, a groupof similar sectorial control electrodes, to which said cathode and anodeare common, disposed in a plane-parallel with said cathode and anode inthe space between said cathode and anode, said control electrodes beingpositioned side by side in a circular array and separated by radialgaps. and screen electrodes disposed partition-wise in said gaps betweensaid control electrodes so as to screen each of them from the others.

4. In an electron discharge device, a substantially flat cathode spacedfrom a substantially fiat cooperating anode parallel therewith, a groupof similar sectorial control electrodes, to which said cathode and anodeare common, disposed in a plane-parallel with said cathode and anode inthe space between said cathode and anode, said control electrodes beingpositioned side by side in circular array and separated by radial gaps,screen electrodes disposed partition-wise in said gaps between saidcontrol electrodes so as to screen each of them from the others, and asecond group of similar sectorial control electrodes disposed in a planeparallel with the first group and in the space between said first groupand said anode with the sectors of the two groups opposite each otherrespectively.

5. In an electron discharge device, a central elongated electronemitting cathode, a group of similar annular control electrodescoaxially surrounding said cathode and spaced apart along its length foreach, independently of the others, to modulate a fraction of theelectron stream emitted by said cathode, a cooperating anode common tosaid group of control electrodes surrounding said group and extendingcoaxially to said cathode to receive the electron stream therefrom, andannular screening electrodes coaxially surrounding said cathode anddisposed partitionwise in the spaces between said control electrodes toform compartments in which said control electrodes are respectivelysituated, to screen each of said control electrodes from the others.

6. In an electron discharge device a central elongated cathode, acooperating anode coaxially surrounding and spaced from said cathode, agroup of similar annular control electrodes, to

which said cathode and anode are common, coaxially surrounding saidcathode and spaced apart along the length thereof, annular screenelectrodes coaxially surrounding said cathode and disposed in the spacesbetween said control electrodes so as to screen each of them from theothers, and a second group of similar annular control electrodesdisposed in the space between said first group and said anode with theelectrodes of the second group coaxially surrounding and lying oppositethe electrodes of the first group respectively.

'7. An electron discharge device as defined in claim 1, in which saidanode is supported by a conductor sealed through one end of the envelopeof the device, the remaining specified electrodes of the device allbeing assembled on and supported by a member sealed to the other end ofthe envelope and constituting a closure therefor.

8. An electron discharge device as defined in claim 2, in which saidanode is supported by a conductor sealed through one end of the envelopeof the device, the remaining specified electrodes of the device allbeing assembled on and supported by a member sealed to the other end ofthe envelope and constituting a closure therefor. 9. An electrondischarge device as defined in claim 3, in which said anode is supportedby a conductor sealed through one end of the envelope of the device, theremaining specified electrodes of the device all being assembled on andsupported by a member sealed to the other end of the envelope andconstituting a closure therefor. 10. An electron discharge device asdefined in claim 4, in which said anode is supported by a conductorsealed through one end of the envelope of the device, the remainingspecified electrodes of the device all being assembled on and supportedby a member sealed to the other end of the envelope and constituting aclosure therefor. 11. An electron discharge device as defined in claim5, in which said anode is supported by a conductor sealed through oneend of the envelope of the device, the remaining specified electrodes ofthe device all being assembled on and supported by a member sealed tothe other end of the envelope and constituting a closure therefor. 12.An electron discharge device as defined in claim 6, in which said anodeis supported by a conductor sealed through one end of the envelope ofthe device, the remaining specified electrodes of the device all beingassembled on and supported by a member sealed to the other end of theenvelope and constituting a closure therefor.

' BADEN J. EDWARDS.

